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Will the FDA Approve VIVUS' Obesity Drug?

All signs point to yes, but the FDA restrictions will be important for commercial success.

I'm going to go out on a limb and say VIVUS' (Nasdaq: VVUS) Qnexa gets approved next week.

I admit I'm now standing on a branch that's 6 inches in diameter and only a foot off the ground, but this is the Food and Drug Administration, after all. Anything is possible.

The confidence in an approval, from me and most of the rest of the investing world, comes from three sources:

The FDA advisory committee gave the drug a resounding 20-2 endorsement back in February.

The FDA delayed the decision in April, which seems like a strange move if the agency had other problems with the drug beyond needing to review the Risk Evaluation and Mitigation Strategy.

And most recently, the FDA approvedArena Pharmaceuticals' (Nasdaq: ARNA) Belviq, signaling an end to the agency's apparent stance that obesity drugs had to be perfect to gain approval.

The smaller, less-stable limb that investors have to venture out on if they want to hold over the binary event is what the REMS will look like. Qnexa will have restrictions on its use -- that's what a REMS is for -- but the different scenarios could have different effects on how well Qnexa sells.

The FDA doesn't want Qnexa prescribed to women who might become pregnant, because one the components of the drug is Johnson & Johnson's (NYSE: JNJ) epilepsy medication Topamax, which has been shown to cause oral clefts in babies of women who took the drug.

How the FDA determines whether patients are pregnant is key to whether the drug is a commercial success. At one extreme, the FDA could simply tell doctors they need to ask female patients whether they're pregnant. At the other extreme, the FDA might require patients to get a monthly pregnancy test from their doctor. The added inconvenience of a monthly trip to the doctor's office could hamper sales. Somewhere in between those extremes, the FDA might be content with self-reporting of a home-based pregnancy test.

The FDA tends to error on the side of caution -- just look at the large preapproval heart trial it's requiring Orexigen Therapeutics(Nasdaq: OREX) do on its obesity drug -- so I think some sort of pregnancy test will be required. Whether it's an overly burdensome requirement remains to be seen, but my guess is that the FDA will be somewhat reasonable given the recent approval of Belviq, which also wasn't a perfect drug (they never are).